Grinding machine

ABSTRACT

The specification discloses a two-press grinding machine for the reduction of wood to small particle sizes. A grinding wheel is fixed to a horizontal shaft and is rotated thereby. Two presses are provided on opposite sides of the wheel to press logs of wood against the periphery of the grinding wheel and the axes of the presses are horizontal and are located above the axis of rotation of the grinding wheel. The location of the press axes above the horizontal plane of the shaft axis has the advantage that the shaft of the grinding wheel in any condition of operation of the machine will always make contact with the lower region of its bearing surfaces while, furthermore, the horizontal arrangement of the presses results in a simple construction of the machine.

ilnitnd Mates Wntent [7 2] Inventors lilelmnt 'lllltntinm;

Willy Sclinlcli, both oll lllleindenheim, Germany {211 App]. No. mliflfittl [22] Filed 1 Nov. 211, NW [45] Patented Dec. 11 1, 119711 [73] Assignee .11. M. l/oitlh Gmnhllil lilleindenheim, Germany [32] Priority Nov. 27, WW 3 Gerinnny [31] 191131111 W'Ltl [54] Glltlhlllllllilfi ll/llAlClllllll'illE 5 Cllnirns, 3 Drawing Figs.

[52] 111.8. (21 Mil/11511 [51] lint. i311 1111mm MW [50] Field ollSmlrcln 241/151, 2 80, 282

[ 5 6] llteliemnces Cited! UNlTED STATES PATENTS 2,588.448 3/1952 Worm 241/151 X Primary Examiner-- Donald G. Kelly Attorney-Melvin A. Crosby AllBS'llliliAtI'l: The specification discloses a two-press grinding machine for the reduction of wood to small particle sizes. A grinding wheel is fixed to a horizontal shaft and is rotated thereby. Two presses are provided on opposite sides of the wheel to press logs of wood against the periphery of the grinding wheel and the axes of the presses are horizontal and are located above the axis of rotation of the grinding wheel. The location of the press axes above the horizontal plane of the shaft axis has the advantage that the shaft of the grinding wheel in any condition of operation of the machine will always make contact with the lower region of its bearing surfaces while, furthermore, the horizontal arrangement of the presses results in a simple construction of the machine.

MEME m z 4 my INVEN'H )R. HELMUT mum BY um swmw onrnntno inner-unis This invention relates to a machine for reducing work material to small particles and particularly to a grinding machine for mechanically grinding logs to produce small wood particles for the manufacture of paper.

Grinding machines for grinding wood to form small particles are ltnown and usually comprise a grinding stone, or wheel, mounted on a horizontal shaft and driven in rotation thereby, and having presses located on opposite sides of the grinding wheel for pressing the logs to be ground against the peripheral surface of the grinding wheel.

in the grinding machine of the nature described. the support shaft of the grinding wheel is subjected to several forces which include the weight of the grinding wheel and the shaft, the pressing forces of the presses which press the logs against the sides of the grinding wheel, and the reaction forces which are set up on the wheel as it rotates against the wood. The lastmentioncd forces are circumfercntially directed and are directed opposite to the direction of rotation of the wheel at the point the forces are created. Since one press is on the upgoing side of the wheel and the other press is on the downgoing side of the wheel, the forces will be directed downwardly and upwardly, respectively. The magnitudes and the specific directions of the pressing and reaction forces will depend upon the locations of the presses and the pressure exerted on the wood by the presses to force it against the wheel.

it is lrnown to locate the presses in such a machine so that the axes along which the forces developed by the presses act are in the same horizontal plane as the axis of the grinding wheel support shaft. in this case the reaction forces are substantially vertically directed and, if the pressure applied on the opposite sides of the wheel are equal, the forces acting on the grinding wheel support-shaft bearings, due to the reaction forces, will exactly cancel out and the bearings will have to bear only the weight of the grinding wheel and its shaft. This weight, of course, bears upon the lower region of the surface of the bearings for the shaft. The line of action of the pressing forces are horizontal and develop no vertical forces on the grinding wheel.

lt inevitably occurs that one or the other of the presses imposes a smaller load on the grinding wheel than the other, either due to the nature of the charges of wood being pressed against the grinding wheel by the respective presses, or due to the fact that one of the respective presses are temporarily idle to receive a new charge ofwood.

When one press is idle, one of the reaction loads is eliminated and, if the one which is eliminated, is on the upgoing side of the wheel, and if, furthermore, the reaction force developed on the downgoing side of the wheel is greater than the weight of the wheel and its shaft, the shaft will be thrust upwardly against the upward region of the shaft support bearings. Due to the tolerances to be found in shafts and bearings, the shaft in such a machine can move upwardly and downwardly and run irregularly and cause inefficient operation of the machine, while, also, special construction of the bearings is required to insure that the upper regions thereof will be properly lubricated.

Another grinding machine construction, which is known, has the presses on the opposite sides of the grinding wheel arranged with their axes located beneath a horizontal plane containing the axis of rotation of the grinding wheel shaft. With this arrangement, the pressing forces of both presses have a component directed vertically upwardly and which counteracts the weight of the grinding wheel and shaft. With this arrangement, the compensation for the weight of the grinding wheel and shaft is rather difficult to obtain and it occurs that there are times when the weight referred to is overcompensated and the shaft is thrust upwardly against the upper region of the bearing surfaces. On the other hand, if the weight referred to it insufficiently compensated, the shaft supporting the grinding wheel will bear on the lower surface. Thus, with this last-mentioned arrangement, the support shaft for the grinding wheel tends to take an oscillatory movement upwardly and downwardly and so that the same defects are encountered as mentioned for the first-mentioned construction.

There is also ltnown a grinding machine having two presses in which the axes of the presses extend downwardly toward the grinding wheel at an angle to the horizontal so that the pressure applied by the worlt on the grinding wheel will always press the grinding wheel downwardly. This type of machine construction, which may be referred to as V-shaped, calls for an inclined construction of the presses, creates problems not only with the construction of the machine but, also, in connection with the lubrication of the sliding surfaces of the presses which are not encountered when the presses are horizontally arranged.

Having the foregoing in mind, a primary objective of the present invention is the construction of a two-press grinding machine of the nature referred to which avoids the difficulties encountered in the prior art as referred to above.

Another object of the present invention is the provision of a two-press grinding machine of the nature referred to having horizontally arranged presses but in which the support shaft of the grinding wheel always engages the lower region of the bearing surfaces therefor.

A particular object of the present invention is the provision of a two-press grinding machine of the nature referred to in which the presses are arranged horizontally but are so posi tioned relative to the support shaft of'the grinding wheel that, even when the press on one side of the grinding wheel is completely idle, thereby creating the most unbalanced operating conditions possible, the shaft of the grinding wheel will make contact with the lower region of the bearing surface therefor.

The foregoing objects, as well as still other objects and advantages of the present invention, will become more apparent upon reference to the following detailed description taken together with the accompanying drawings, in which:

lFlG. l shows one-half of a two-press grinding machine according to the present invention, in section, with the other half of the grinding machine forming a mirror image of the half which is illustrated;

H6. 2 is a schematic view showing vectors of the forces which act on the grinding wheel; and

H6. 3 is a force diagram showing the vertically directed forces acting on the grinding wheel when one press is idle.

BRlEF SUMMARY OF THE. INVENTION The present invention solves the problem of insuring that the support shaft for the grinding wheel of a two-press grinding machine will always engage the lower region of its support bearings by arranging the press on the downgoing side of the wheel substantially horizontally and with the axis along which the force developed thereby acts arranged above the axis of rotation of the grinding wheel.

The reaction force acting on the grinding wheel due to its rotation against the work members in the press on the downgoing side of the grinding wheel is: directed upwardly tangentially to the wheel at an angle to the vertical so as to have both vertical and horizontal components.

The pressing force which the press errerts on the downgoing side of the wheel also has a vertical component which is, however, directcd downwardly opposite to the direction of the vertical component of the reaction force due to grinding. Because of the above-mentioned combination of forces acting on the downgoing side of the wheel, even if the pressing force is released from the opposite side, namely, the upgoing side of the wheel, the downwardly directed component of the pressing force at the downgoing side of the wheel, together with the weight of the grinding wheel and its shaft will be suffi cient to hold the shaft downwardly against the lower region of its support bearings.

The shaft is, therefore, prevented from ever moving vertically and contacting the upper region of its bearing surfaces but will always ride on the lower region of the bearing surfaces whereby both lubrication and construction of the bearings is simplified, and the machine runs more quietly and produces a product of uniform quality under stable, reliable operating conditions.

Both of the presses according to the present invention are arranged horizontally, which yields the most simple and reliable construction. The vertical spacing between the horizontal plane in which the grinding wheel shaft axis is disposed and the horizontal plane in which the pressing force of the press on the downgoing side of the wheel acts is advantageously from about one-twentieth to one-fourth of the diameter of the grinding wheel.

While the press on the downgoing side of the grinding wheel must, according to the present invention, be located above the level of the axis of the grinding wheel shaft, the press on the opposite upgoing side of the wheel can vary in height from below the horizontal plane of the axis of the grinding wheel shaft to above it. The construction of the grinding machine is simplified when both presses are arranged at the same level on opposite sides of the grinding wheel and with the axes along which the respective pressing forces act being in alignment with each other.

While the present invention is illustrated in particular with presses actuated by fluid motors, it will be apparent that other pressure members, e.g., endless travelling chains can be employed. It is only essential that the grinding wheel exhibits two working regions on respectively opposite sides of the center of rotation thereof.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings somewhat more in detail, in FIGS. 1 and 2 the grinding machine will be seen to comprise a rotatable shaft extending horizontally and mounted in support bearings which are not shown. A grinding wheel 11 is mounted on the shaft and on the left side thereof is arranged a press I and on the other side is press II. The central axes of the press are horizontal and coaxial and are located in a horizontal plane spaced upwardly from the horizontal plane containing the axis ofshaft 10.

The essential elements of each press, as will be seen in FIG. I, include a press plunger 12 mounted on the end ofa ram 13, forming a part of a double-acting fluid motor 14. Logs to be ground are disposed between plunger 12 and the periphery of grinding wheel 11. A supply of the logs may be disposed in hopper I5 and fed into the space ahead of plunger 12 by retraction of sliding gate 16 by a second double-acting fluid motor 17. I

The bottom plate 18 of the press, which carries a lip at its inner end adjacent grinding wheel 11, is advantageously adjustable toward and away from the grinding wheel.

The machine includes spaced sideplates 20 and extending therebetween on each side of the wheel is a crossbeam 21, fixed to the sideplates, and on the bottom side of which rests a horizontal shiftable carrier 22, which also has a lip on the wheel side extending toward the wheel.

Reference to FIG. 2 will shown the forces which act upon grinding wheel 11.

In each of the presses I, ll, there is an applied pressure P,, P,, respectively, which are directed horizontally toward each other but which, due to the location of the press axes above the axis of revolution of the grinding wheel result in the forces R,, R, acting on the grinding wheel. Forces R and R, can be resolved into horizontal and vertical components. Thus, pertaining to force R is the horizontal component identified as P, and the vertical component identified as P Similarly, for force R, there is the horizontal component P and the vertical P Identified at G is a downwardly directed vector representing the weight of the grinding wheel and the supporting shaft therefor. Furthermore, at the downgoing side of the wheel, and tangentially directed, is the reaction force represented by vector U,, which can be resolved into a vertical component U and a horizontal component U Also, on the upgoing side of the wheel will be found a tangentially directed reaction force identified by vector U,, which can be resolved into a vertical component U and a horizontal component U It will be recognized that under conditions of uniform loading on opposite sides of the grinding wheel, the force vectors P and P cancel each other out, while the force vectors U, and U are additive, but amount to a small force only. The vertically directed force vectors P and P are additive and add to vector G to give the downward force on the shaft of the grinding wheel.

The force vectors U and U under the described conditions will be equal and will cancel out in respect of imposing any vertical load on the shaft of the grinding wheel and will merely exert a torque on the grinding wheel opposite to the direction of rotation thereof.

The most extreme conditions of operation occur when the pressing force P, of press II is discontinued. Under these circumstances, only the vector G and the force vectors, due to applied pressure P of press I will act on the grinding wheel.

As shown in FIG. 3, the vertical component P and the force vector G are additive to produce a downwardly directed force and the upwardly directed force vector U, is subtracted therefrom leaving a resultant force vector R which acts downwardly.

It will, therefore, be seen that, even in the most unfavorable condition of operation of the two-press grinding machine according to the present invention, the grinding wheel and its shaft will be subjected to a downwardly directed force causing the shaft to engage the lower regions of its support bearings. In all other conditions of operation, of course, the downwardly directed force acting on the grinding wheel and its shaft is even larger than the resultant R illustrated in FIG. 3 and representing the most unfavorable condition of operation of the machine.

It will be understood that modifications can be made within the scope of the appended claims.

What is claimed is:

I. In a machine especially adapted for reducing wood to small particle size: a cylindrical tool mounted for rotation on a horizontal axis and having an upgoing lateral side and a downgoing lateral side when viewed in the axial direction, press means on each said lateral side of said tool for receiving work members to be worked and including pressure means for pressing the work members against the respective lateral side of the tool, each press means having a substantially horizo ntal central work axis along which the force exerted on the work members therein by the respective pressure member acts, and at least that press means which is disposed on,the downgoing side of said tool having the said central workaxis disposed in a substantially horizontal plane which is ,located a predetermined distance above the horizontal plane which contains the axis of rotation of said tool, said predetermined distance being such that the summation of the vertical components of the forces acting on the downgoing lateral side of the tool due to the work members pressed thereagainst during rotation of the tool never exceeds the gravitational force acting on the tool.

2. A machine according to claim 1, in which said tool is in the form of a grinding wheel.

3. A machine according to claim 2, in which the plane of the central work axis of the press means on the downgoing side of said grinding wheel is spaced upwardly from the said horizontal plane containing the axis of rotation of said grinding wheel a distance of from about one-twentieth to about one-fourth of the diameter of said grinding wheel.

4. A machine according to claim I, in which the central work axes of said press means are disposed in a common substantially horizontal plane located above the said horizontal plane containing the axis of rotation of said tool.

5. A machine according to claim 1, in which said tool is a grinding wheel and each said press means comprises a boxlike holder for logs and open on the side facing said grinding wheel, a plunger in each holder reciprocable therein in a direction toward the open side thereof and adapted for pressing logs in the respective holder against the respective lateral side of the grinding wheel, each said plunger exerting a force on the logs in the respective holder which acts in a submeans for retracting said plungers independently to permit logs to be ground to be introduced into the respective holders between the said plunger therein and the respective lateral stantially horizontal plane substantially centrally located with 5 slde of the grinding wheel' respect to the vertical height of the respective holder, and 

1. In a machine especially adapted for reducing wood to small particle size: a cylindrical tool mounted for rotation on a horizontal axis and having an upgoing lateral side and a downgoing lateral side when viewed in the axial direCtion, press means on each said lateral side of said tool for receiving work members to be worked and including pressure means for pressing the work members against the respective lateral side of the tool, each press means having a substantially horizontal central work axis along which the force exerted on the work members therein by the respective pressure member acts, and at least that press means which is disposed on the downgoing side of said tool having the said central work axis disposed in a substantially horizontal plane which is located a predetermined distance above the horizontal plane which contains the axis of rotation of said tool, said predetermined distance being such that the summation of the vertical components of the forces acting on the downgoing lateral side of the tool due to the work members pressed thereagainst during rotation of the tool never exceeds the gravitational force acting on the tool.
 2. A machine according to claim 1, in which said tool is in the form of a grinding wheel.
 3. A machine according to claim 2, in which the plane of the central work axis of the press means on the downgoing side of said grinding wheel is spaced upwardly from the said horizontal plane containing the axis of rotation of said grinding wheel a distance of from about one-twentieth to about one-fourth of the diameter of said grinding wheel.
 4. A machine according to claim 1, in which the central work axes of said press means are disposed in a common substantially horizontal plane located above the said horizontal plane containing the axis of rotation of said tool.
 5. A machine according to claim 1, in which said tool is a grinding wheel and each said press means comprises a boxlike holder for logs and open on the side facing said grinding wheel, a plunger in each holder reciprocable therein in a direction toward the open side thereof and adapted for pressing logs in the respective holder against the respective lateral side of the grinding wheel, each said plunger exerting a force on the logs in the respective holder which acts in a substantially horizontal plane substantially centrally located with respect to the vertical height of the respective holder, and means for retracting said plungers independently to permit logs to be ground to be introduced into the respective holders between the said plunger therein and the respective lateral side of the grinding wheel. 